1. Field of the Invention:
This invention relates to a pressing station for metal foil sheets placed around the top and the neck of bottles in a labelling machine with a transfer station located on the turntable for the bottles which transfers the metal foil sheets to the bottles, and a delivery star wheel, in which corresponding to each receiving spot for the bottles there is a bell-shaped pressing element which can be moved axially by a cam controlled drive mechanism toward the bottle top, wherein the pressing element is held by a support located above the delivery star wheel and which rotates with the delivery star wheel.
2. Description of the Prior Art:
On such pressing stations, the rotating paths of the delivery positions of the turntable and of the delivery star wheel overlap, so that the bottles can be transferred in synchronization from the turntable to the delivery star wheel. Since during transport of the bottles both in the turntable and in the delivery star wheel, elements grip the top of the bottle, namely centering heads when the bottle is on the turntable and pressing elements when the bottle is in the delivery star wheel, it is difficult to achieve a collision-free fit of the elements of the turntable and of the delivery star wheel in the overlapping region. Since for purposes of a transfer of the bottles from the turntable to the delivery star wheel at the proper angle of rotation, the bottles in the turntable must be held as long as possible in a rotation-free manner by axial bracing between the turntable which supports the bottom of the bottle, and a centering element which grips the top, for a collision-free passage of the pressing elements of the delivery star wheel, it is necessary to move these pressing elements out of the overlapping area during the passage.
In a pressing station of the prior art (German Laid Open Patent Appln. No. 31 04 807 C2, which corresponds to U.S. Pat. No. 4,414,056 the disclosure of which is incorporated herein by reference), this problem is approached by equipping each pressing element so that it can pivot to one side from its position above the receiving position, into a position which lies outside the portion of the turntable traversed by the centering head of the turntable. Only when the pressing element has passed the overlapping area can it be pivoted over the bottle top of the corresponding receiving position, and then lowered to press the foil sheet. One disadvantage of such pressing stations is that a great deal of space is required for the pivoting movement, and the drive and transmission mechanisms required for the pivoting motion and the subsequent axial movement are quite complex and expensive.
These disadvantages related to the pivoting movement do not occur on another pressing station of the prior art (German Laid Open Patent No. 35 15 730 A1, the disclosure of which is incorporated herein by reference), in which the pressing elements are located so that they pivot on the circumference of a support, which has a smaller diameter than that of the delivery star wheel, and is mismatched in relation to the delivery star wheel such that the path of the pressing elements lies outside the path of the receiving positions of the turntable, and only above a short segment of the path of the receiving positions of the delivery star wheel. A disadvantage, however, is that synchronization between the receiving positions of the delivery star wheel and the pressing elements can only be achieved over the above-mentioned short segment, and then only approximately, which has a negative effect on the quality of the pressing of the foil sheet.
On both pressing stations of the prior art, however, a collision-free passage of the pressing elements on the delivery star wheel and the centering heads on the turntable or synchronization between the receiving positions of the delivery star wheel and the pressing elements is only guaranteed during operation when there is no daming up at the outlet of the delivery star wheel. To prevent major damage to the pressing station when there is a jamming up at the outlet of the delivery star wheel, the delivery star wheel is coupled in pressing stations used in practice with the drive by means of a slip clutch. If a jamming up does occur, then the delivery star wheel can slip in relation to the drive. In the first pressing station of the prior art described above, that leads to pivotable pressing elements which are oriented concentrically to the receiving positions, so that the synchronization between the turntable and the pressing elements is lost. When rotation continues, therefore, even with the pressing elements pivoted back, collisions occur. In the other pressing station of the prior art described above, with the support for the pressing elements offset and not torsionally connected to the delivery star wheel, a slipping of the delivery star wheel in relation to the drive as a result of a jam leads to an offset between the receiving positions and the pressing elements corresponding to the receiving positions in the pressing area. Once again, the result is that the pressing elements can no longer be placed centrally over the bottle tops.